cant control where heat blows to

[sheffy]

so my 97 gt 3800 is having some sort of problem with the part that controls where the heat is directed to. i pulled the control unit out of the dash and it has about 6 tubes of various colors connected. tried to block the holes with my fingers and it did nothing. Where do I look to fix this issue?? i need to be able to direct where the air goes....

thanks in advance